[asan] move {linux,mac}-specific code from asan_thread.cc to asan_{linux,mac}.cc; also add asan_procmaps.h which I forgot to add on previous commit.

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@147586 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed